I too install in house on all my builds. I use TechLine Coatings. They have a water based and solvent based coatings. Yes, the materials are cheap. The labor to properly prep parts is where the cost is. I charge actual time or prep surcharge if used parts. The process is something like this: (media blast, clean, prebake, clean, blast , clean, warm, coat, clean, burnish) you get the idea. Time at each step.
In a build with full parts coatings the list would look something like this. I agree that the more stress you put on the engine (compression, displacement, rpm range, etc) the more the benefit of the coatings from safety margin, friction reduction and heat management.
Examples of parts for DFL:
Main bearings
Layshaft bearings
Rod bearings
rocker shafts
Cam lobes and journals
piston skirts
wrist pins
Basically any part that has friction.
I have also DFL coated cam sprockets, Intermediate shaft gears, etc
Oh, and don't forget transmission parts.
TBC coated parts include:
Cylinder head chambers
Exhaust ports
Exhaust valves
Piston crowns
Valve faces.
I typically do not coat the intake ports. I think a little heat helps in vaporization.